Upgrading is generally always safe (between many minor and one major version) and dashboards and graphs will look the same. There can be minor breaking changes in some edge cases which are usually outlined in the [Release Notes](https://community.grafana.com/c/releases) and [Changelog](https://github.com/grafana/grafana/blob/master/CHANGELOG.md)
Before upgrading it can be a good idea to backup your Grafana database. This will ensure that you can always rollback to your previous version. During startup, Grafana will automatically migrate the database schema (if there are changes or new tables). Sometimes this can cause issues if you later want to downgrade.
One of the database migrations included in this release will update all annotation timestamps from second to millisecond precision. If you have a large amount of annotations the database migration may take a long time to complete which may cause problems if you use systemd to run Grafana.
We've got one report where using systemd, PostgreSQL and a large amount of annotations (table size 1645mb) took 8-20 minutes for the database migration to complete. However, the grafana-server process was killed after 90 seconds by systemd. Any database migration queries in progress when systemd kills the grafana-server process continues to execute in database until finished.
If you're using systemd and have a large amount of annotations consider temporary adjusting the systemd `TimeoutStartSec` setting to something high like `30m` before upgrading.